reciprocating engine or combustion turbine?
TRANSCRIPT
Reciprocating Engine or Combustion Turbine?
Coauthors: Kurt Koenig
Grant Ericson
AGENDA
► Installations
► Technology Overview
► Footprint
► Performance
► Power to Heat Ratio
► Thermal Load Following
► Fuel Flexibility
► Emissions & Permitting
► Vibrations & Acoustics
► Capital Costs
► O&M Costs
► Decision Matrix
► Case Study
TECHNOLOGY OVERVIEW
► Gas turbines (4-50+ MW)
► Reciprocating engines (2-18 MW)
3
turbocharger generator
block, pistons, cylinders, rods, crankshaft
air inlet
head, valves, rockers, springs air inlet
compressor
generator
turbine
combustor
GE Jenbacher 616 Solar T70
CTG/REG INSTALLATION
► CTG installation more abundant
► Large REG installation popularity growing, still significant number of installations
► CHP market in US dominated by turbines
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FOOTPRINT
► For smaller applications footprints are similar
► For larger applications, footprint of CTG smaller than REG
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7.5MW Recip 7.5MW CTG
17MW Recip 15MW CTG
51MW Recip 50MW CTG
50’
PERFORMANCE
Considering the previous REG/CTG comparisons:
*Heat rate of REGs generally much lower than CTG counterpart
*Thermal (exhaust) output of REGs generally much lower than CTG counterpart
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Unit Power Output (MW)
Heat Rate (BTU/kWh, LHV)
Exhaust Gas Flow (lb/hr)
Exhaust Gas Temperature (°F)
7.5 MW REG 7.5 7,400 94,000 734
7.5 MW CTG 7.5 10,100 214,000 960
17 MW REG 17 7,100 246,000 707
15 MW CTG 15 9,700 395,000 940
3 x 17 MW REG 51 7,100 737,000 707
50 MW CTG 50 7,100 1,100,000 890
PERFORMANCE
► Power to heat ratio
► Selecting the appropriate prime mover allows the
best utilization of capital with the ability to base load
the equipment.
• REGs range from 1.0 to 1.5.
• CTGs range from 0.55 to 0.74.
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REG
MW Total Heat
MWt Power /
Heat
4.0 3.8 1.041
4.5 4.2 1.071
5.4 3.7 1.456
6.5 5.8 1.123
7.4 4.9 1.523
CTG
MW Total Heat
MWt Power /
Heat
3.5 6.3 0.553
4.6 7.8 0.590
5.7 8.9 0.638
6.3 9.5 0.666
8.0 10.9 0.736 0
5
10
15
20
25
4 5 6 7 8 10 12 15
MW
Th
erm
al
MW Electric
PERFORMANCE: THERMAL LOAD
FOLLOWING
► Exhaust gas bypass damper:
► CTG: on/off, REG: modulating
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CBPG HRSG with Bypass, Ex Louver Shown
PERFORMANCE: THERMAL LOAD
FOLLOWING CTG
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Thermally limited: add steam drive chiller (or other steam sink)
PERFORMANCE: THERMAL LOAD
FOLLOWING REG
► Modulating exhaust gas bypass
damper prevents shutdown due to
lack of thermal load
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FUEL FLEXIBILITY
► Generally, REG’s only operate on gaseous or liquid fuel; fuel type specifies machine
type.
• Few units available to operate on gaseous and liquid fuel
• Propane operation requires 25%+ electrical derate
► Generally, CTG’s capable of consuming wide variety of gaseous/liquid fuels
• Certain fuels may dictate
higher emissions
combustors
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Gaseous Liquid
Natural Gas Light Fuel Oil
Propane Heavy Fuel Oil
Syngas Crude Oil
Landfill Gas Fuel Water Emulsion
Process Off Gas Liquid Biofuel
Digester Gas
EMISSIONS & PERMITTING
► Generally, CTGs offer lower emissions than REG counterparts
► SCR can reduce CO, Nox by 80-90%
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Peerless SCR
VIBRATIONAL & ACOUSTICAL
► CTG Vibration
• Typically manageable
► Sound
• Sound-attenuating enclosures
• Intake air silencers
• Exhaust gas silencers
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Anti-vibration mount IAC Exhaust Silencer CTG Enclosure
► REG Vibration
• Anti-vibration mounts
• Isolating pads
► Sound
• Smaller units enclosed
• Intake air silencers
• Exhaust gas silencers
CAPITAL COSTS
► Among smaller options (<5 MW), capital costs are similar between CTGs, REGs (no
BOP considered).
► Among larger options, capital costs of CTGs are less.
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O&M COSTS
► Variable O&M
• Minor maintenance
• Lube Oil Consumption (REGs)
• SCR Reagent Consumption
• Major Maintenance
► Fixed O&M
• Plant Operations
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O&M COSTS
O&M Cost Differences
► Variable O&M
• Overhaul may fall under separate
contract for REGs
• Trained plant operators may
perform minor REG maintenance
• REG O&M costs vary largely
between manufacturers
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► Variable O&M costs:
• REG $0.005/kWh-$0.010/kWh
• CTG $0.007/kWh-$0.011/kWh
DECISION MATRIX
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Points Criteria REG CTG
Weight: [ 5 ] Range: 0-5
Q: What is the power to heat ratio? (kW * 3412) / (BTU/H). Score: Ratio of 1.0 to 1.5+, all points to REG
Ratio of <0.55 to 0.74, all points to CTG
Weight: [ ] Range: 0-5
Q: What is the impact of space? Score: If greenfield site or size < 20 MW REG & CTG = 50% * Weight. If existing site, size > 20 MW, tight plant arrangement REG = 25% * Weight, CTG = 75% * Weight
Weight: [ ] Range: 0-5
Q: What fuel diversity is required? Score: If gaseous and liquid fuel desired REG = 25% * Weight, CTG = 75% * Weight. Else REG & CTG = 50% * Weight
Weight: [ ] Range: 0-5
Q: What startup time is required? Score: If less than five minutes all points to REG. Else REG & CTG = 50% * Weight
Weight: [ ] Range: 0-5
Q: What level of emissions is desired? Score: If permitting process difficult and tight emission tolerances required CTG = 75% * Weight. Else REG & CTG = 50% * Weight
Weight: [ ] Range: 0-5
What concern is plant vibration and acoustics? Score: If plant vibration and acoustics are major concerns CTG = 75% * Weight. Else REG & CTG = 50% * Weight
Totals
